Relationship of Runoff Coefficient with The Surface Soil Moisture and Groundwater Level (Case Study: Ajabshir Basin)

Reduction of rivers inflow which discharge to reservoirs of the country such as Lake Urmia is the most important present problem of water industry. so the role of runoff coefficient to determine the runoff arising from precipitation in order to anticipate and manage the stream flow is of great importance.Soil moisture, especially surface soil moisture, plays an important role in the natural water cycle in nature particularly in the distribution of rainfall and its turn into runoff and infiltration. On the other hand, stream flow always affects the level of the groundwater table. Therefore, the relationship between the runoff coefficient with surface soil moisture and water table level in order to determine the volume of runoff arising from precipitation can be one of the most important issues in the field of water resources management. In this study, MODIS satellite images were used to estimate the spatial and temporal variations of soil moisture and relationship between instantaneous runoff coefficient (events) and daily groundwater table level, as well as its relation with daily surface soil moisture extracted from the atellite images for the two hydrometric stations located at the beginning and end of the Ghaleh _Chay river discharging into the Lake Urmia were investigateResults of this research confirmed the existence of a direct relationship between the runoff coefficients and water table at the Shishavan and Yengejeh stations with a correlation coefficient 0.9 and 0.84 respectively.Also direct connection between the runoff coefficient and daily surface soil moisture was registered with correlation coefficient of 0.792 and 0.815 at the stations of Shishavan and Yengejeh, respectively.